The present invention relates to a semiconductor device and a power conversion apparatus using the same, and in particular to a semiconductor device preferred for an insulated gate bipolar transistor (hereinafter abbreviated to IGBT) having an insulated trench gate structure and a power conversion apparatus using the same.
The IGBT is a switching device for controlling a current to be flown between a collector electrode and an emitter electrode in response to a voltage applied to a gate electrode. Since electric power to be controlled by IGBT is ranged from several tens to several hundred thousand watts and switching frequency is ranging from several tens to over hundred kilohertz, the IGBT has been widely used from low electric power devices, such as an air-conditioner, microwave oven, etc. for household use to high electric power devices, such as an inverter for use in railroad rolling stock, steel plant, etc.
For the purpose of realizing a high efficiency operation of the electric devices, IGBT has been demanded for a low loss, that is, demanded for reduction of a conduction loss and a switching loss. At the same time, it has been demanded that dv/dt can be controlled to fit a specification for an application so as to prevent a problem, such as EMC noise, malfunction, breakdown of motors, etc.
Incidentally, JP-A-2000-307116 discloses IGBT having a structure in which an arrangement pitch of a trench gate is changed, as illustrated in FIG. 23. A feature of the IGBT in FIG. 23 is that a floating p-layer 105 is formed on a portion where the interval between the trench gates is wide, without forming a p-channel layer 106.
In the configuration as mentioned above, since a current is only flown into a portion where the interval between the trench gates is narrower, an over current flowing at a short circuit can be inhibited, therefore, a ruggedness of the device can be improved. Further, since a part of a hole current flows into an emitter electrode 114 via the floating p-layer 105, a hole concentration increases around the emitter electrode 114, therefore, there is also an advantage that an on-state voltage can be reduced. Furthermore, there is also an advantage that an electric field applied to the trench gate is relaxed by a p-n junction formed of the floating p-layer 105 and an n− drift layer 104.